This invention relates generally to the cleaning of semiconductor materials and specifically to the post silica polish cleaning of semiconductor wafers.
With the advent of microminiaturization of electronic devices, the need for damage-free, smooth and clean semiconductor wafer surfaces has become increasingly important. Smooth, polished surfaces are obtained by the use of polishing slurries. Silica polishing is an example of a typical polishing process. In the silica polishing process, a polishing slurry is used which includes a colloidal silicon dioxide abrasive, sodium dichloroisocyanurate as an oxidizing agent, and sodium carbonate as a base. The pH of the polishing slurry is below 10. After polishing, it is necessary to clean the polished surface to remove the polishing slurry and other surface contaminants with a minimum of chemical or mechanical surface damage.
At the end of the silica polishing process, removal of the following materials from the wafer surface must be considered in order to produce a clean surface:
1. Colloidal silicon dioxide.
2. Sodium dichloro-isocyanurate and its reaction products with sodium carbonate.
3. Sodium carbonate.
4. Amorphous silicon dioxide.
5. Other metallic impurities deposited on silicon surfaces from slurry components.
Various mechanical and chemical processes have been used to clean silica or other metal oxide based slurry polished wafers. These processes either produce mechanical damage, change the surface characteristics significantly, or use chemicals which present environmental and/or hygienic considerations.
In my copending application Ser. No. 670,508, filed Mar. 25, 1976, now U.S. Pat. No. 4,050,955, an oxidizing agent treatment is discribed using, for example, a NaClO followed by an NH.sub.4 OH rinse.
In my copending application Ser. No. 799,886, filed May 23, 1977, a process is described which uses quarternary ammonium salts to obtain a clean, hydrophobic semiconductor surface without damaging the surface.
A new, environmentally safe and effective method has been found to remove silica polishing materials which provides a clean, damage-free hydrophillic semiconductor surface.